This invention relates to a color separation circuit for use in, for example, a color television receiver.
Conventionally, in a color television receiver, color television monitor, etc., a CCD type comb filter circuit is employed for separating a luminance signal EY and color difference signal EC from a composite video signal of NTSC system. This type of comb filter circuit, as shown in FIG. 1, comprises a delay circuit 10 for delaying the input video signal supplied to an input terminal T1 by one horizontal scanning time period, an adder circuit 12 for adding up the input video signal and the output signal of the delay circuit 10, a subtracter circuit 14 for obtaining a difference between the input video signal and the output signal of the delay circuit 10, a low-pass filter 16 connected to the adder circuit 12 through a delay correction circuit 18, and a band pass filter 20 connected to the subtracter circuit 14. The low-pass filter 16 is used to separate a luminance signal by EY having a bandwidth of 0 to 4 MHz from the output signal of the adder circuit 12, while the band pass filter 20 is used to separate a color difference signal EC having a bandwidth of 3.58 MHz .+-. 0.5 MHz from the output signal of the subtracter circuit 14. The delay correction circuit 18 is used for correcting the difference in time delay between the output signals of the low-pass filter 16 and the band pass filter 20. Note here that in the Figure, the circuits 10, 12, 14 and 18 are constructed in the form of a charge coupled device (CCD), which is driven by a clock pulse generated in synchronism with a burst signal of the input video signal.
The above-mentioned CCD comb filter circuit shown in FIG. 1 functions to separate the luminance signal EY from the input video signal to generate the same from the output terminal T2 and also separate the color difference signal EC from the input video signal to generate the same from the output terminal T3. The CCD comb filter circuit, however, does not have the function of demodulating the color difference signal EC.